1. Field of the Invention
The present invention relates to an image reading apparatus and a copying apparatus having the image reading apparatus.
2. Description of Related Art
In an image reading apparatuses for reading double sided original documents, there is a type of reading apparatus in which reading sections are provided at both sides of original document transport path, and by passing the original document through the transport path once, double face reading is conducted.
Patent Document 1 proposes to improve reliability of the image reading apparatus by taking a countermeasure in cases where a reading section is in failure to make reading impossible.
Failures in reading sections are generated, for example, by a failure of image capturing element or attachment of dust such as paper dust on platen glass. In a reading apparatus employing two reading sections, since a failure of any one of the reading sections causes inability of apparatus operation, probability of breakdown by failure becomes twice the case of a reading apparatus employing one reading section, this decreases reliability of the apparatus.
Therefore, such a countermeasure as disclosed in Patent Document 1 is needed.
Patent Document 1: Unexamined Japanese Patent Application Publication No. 2002-354192
In the technology disclosed by Patent Document 1, in cases of double face reading when one of the reading sections is in failure, since an original document is carried to pass three times through a reading position, the reading efficiency is remarkably decreased when one of the reading sections is in failure, which is a problem.
Particularly for the performance, not as an image reading apparatus itself but as a copying apparatus where the image reading apparatus is combined with an image forming apparatus, there is a problem described below.
In cases where the image reading apparatus conducts double face reading by using two reading sections, and the image forming apparatus conducts double face image formation by using reversing transport path, since image forming speed of the image forming apparatus is usually lower than image reading speed of the image reading apparatus, copying operation is conducted according to the image forming speed of the image forming apparatus, the performance of high reading speed in the reading apparatus is not utilized enough. Further, in cases where one of the reading sections is in failure, since the reading speed of the reading apparatus is extremely lowered, the speed performance of the image forming apparatus cannot be utilized.
As the result, the performance of the copying apparatus becomes unsatisfactory.
Further, in the image reading apparatus disclosed by Patent Document 1, in case of failure at one reading section, since reversal transportation of the original document becomes necessary even when single face reading, the problem of decreased reading speed arises.